Abstract: Abstract: According to the shielding calculation formula of γ point source, the conversion formula on examining the shielding effect of PET special box is deduced using 137Cs point source to substitute 18F. In view of the proportional relationship between the dose equivalent rate and the activity of γ point source, the dose equivalent rate in the reference point is calculated in maximum activity of 18F. The shielding effect of the PET special box can be evaluated by means of calculated result of the conversion formula.